Submillimeter spectroscopy of the magneto- and electrodipolar excitations in rare-earth orthoferrites

We have investigated magneto- and electrodipolar excitations within the Tm 3+ ion ground multiplet in TmFeO 3 orthoferrite. The temperature dependences of the resonance frequencies, the linewidths and the mode contributions to the static magnetic permeability and dielectric permittivity were derived. An increase (up to 30%) of the quasistatic dielectric permittivity along the c-axis was observed at low T resulting from an appreciable contribution of the electrodipolar rare-earth modes in Tm 3+ .